{"id":"CVE-2026-98866","summary":"sched/cache: Introduce task_struct-\u003esched_cache_grp to fix UAF","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched/cache: Introduce task_struct-\u003esched_cache_grp to fix UAF\n\nAdd a sched_cache_grp pointer to task_struct so that scheduler code\ncan access the cache group directly via the task, without going\nthrough mm-\u003esched_cache_grp.  This decouples the scheduler's hot-path\naccesses from the mm_struct.\n\nEach task holds its own refcount on the sched_cache_group, separate\nfrom the reference held by its mm_struct.  The reference is acquired\nin copy_mm() (fork) and exec_mmap() (exec), and released in exit_mm().\nThis fixes the use-after-free when account_mm_sched() reaches the group\nthrough a task whose mm is being switched, as reported by Hyunwoo:\n\n  https://lore.kernel.org/lkml/apPb-Dr4nPYuHQOK@v4bel/\n\nConvert all scheduler code in fair.c and exit.c to use\np-\u003esched_cache_grp instead of p-\u003emm-\u003esched_cache_grp.\n\nKeep the fork/exec/exit reference management out of the generic mm\npaths: add sched_cache_fork(), sched_cache_fork_cleanup(),\nsched_cache_exec_mmap() and sched_cache_exit_mm() in\nkernel/sched/cache_sched.c (with empty stubs for !CONFIG_SCHED_CACHE),\nso fs/exec.c, kernel/fork.c and kernel/exit.c each call one helper\ninstead of open-coding the refcounting under #ifdef.  Also add\nsched_cache_group_get() and task_cache_group_get().","modified":"2026-10-19T02:46:06.408592542Z","published":"2026-10-18T15:51:27.883Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98866.json"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9436130e6da72af63289a4acb3aa0c1df07a3928"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b636fef85bda7d1bab9c0a45067ab1508d79d946"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98866.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98866"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"df0d98475954d655571979aa061ecb07d7e00392"},{"fixed":"9436130e6da72af63289a4acb3aa0c1df07a3928"},{"fixed":"b636fef85bda7d1bab9c0a45067ab1508d79d946"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98866.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.2.0"},{"fixed":"7.2.10"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98866.json"}}],"schema_version":"1.9.0"}